CN111614169A

CN111614169A - Coil selected Q factor determination

Info

Publication number: CN111614169A
Application number: CN202010113234.2A
Authority: CN
Inventors: N·W·史密斯
Original assignee: Aidi Technology Co ltd
Current assignee: Aidi Technology Co ltd; Renesas Electronics America Inc
Priority date: 2019-02-25
Filing date: 2020-02-24
Publication date: 2020-09-01
Also published as: KR20200104233A; US11336119B2; US20200274396A1

Abstract

The application relates to a Q factor determination for coil selection. According to an embodiment of the present invention, a wireless power transmitter includes: a transmit coil comprising a plurality of concentric coils; a switching circuit coupled to the plurality of concentric coils; a driver coupled to provide a voltage to the switching circuit; and a controller coupled to the switching circuit, the controller providing a control signal to the switching circuit based on a Q factor dependent on the measurement in the presence of the receive coil such that the switching circuit selects a voltage to be provided across one or more of the plurality of concentric coils. A method of operating a wireless power transmitter, comprising: determining a measured Q factor for each of a plurality of configurations of concentric transmit coils; determining a difference between each of the measured Q factors and a standard Q factor; and selecting one of a plurality of configurations based on the difference.

Description

Coil selected Q factor determination

Technical Field

Embodiments of the present invention relate to wireless power systems, and more particularly, to backchannel communication in wireless power transmission systems.

Background

Mobile devices, such as smart phones, tablet computers, wearable devices, and other devices, increasingly use wireless charging systems. In general, wireless power transfer involves a transmitter driving a transmit coil and a receiver having a receive coil that is placed in proximity to the transmit coil. The receive coil receives the wireless power generated by the transmit coil and uses the received power to drive a load, e.g., to provide power to a battery charger.

There are currently a number of different standards for wireless transmission of power. More common criteria for wireless transmission of power include: the wireless power alliance (A4WP) standard and the wireless charging alliance (WPC) standard (Qi standard). Under the wireless charging alliance (Qi specification), a resonant inductive coupling system is utilized to charge a single device at the resonant frequency of the receiver coil circuit. In the Qi standard, the receiving device coil is placed in close proximity to the transmitting coil, whereas in the A4WP standard, the receiving device coil is placed in the vicinity of the transmitting coil, possibly together with other receiving coils belonging to other charging devices.

In general, a wireless power system includes a transmit coil driven to produce a time-varying magnetic field and a receive coil, which may be part of a device such as a cellular telephone, PDA, computer, or other device, positioned relative to the transmit coil to receive power transmitted in the time-varying magnetic field.

Therefore, there is a need to develop better coil techniques for wireless power systems and improve sensing of objects placed above the transmitter pad.

Disclosure of Invention

According to an embodiment of the present invention, a wireless power transmitter includes: a transmit coil comprising a plurality of concentric coils; a switching circuit coupled to the plurality of concentric coils; a driver coupled to provide a voltage to the switching circuit; and a controller coupled to the switching circuit, the controller providing a control signal to the switching circuit such that a voltage is selected to be provided across one or more of the plurality of concentric coils depending on the Q factor measured in the presence of the receive coil. A method of operating a wireless power transmitter, comprising: determining a measured Q factor for each of a plurality of configurations of concentric transmit coils; determining a difference between each of the measured Q factors and a standard Q factor; and selecting one of the plurality of configurations based on the difference.

These and other embodiments are further discussed below with reference to the figures.

Drawings

Fig. 1 illustrates a wireless power transmission system according to some embodiments of the present invention.

Fig. 2A, 2B, and 2C illustrate plan views of transmit coils in relation to various receive coils, according to some embodiments.

Fig. 3A and 3B illustrate example transmit coil configurations in accordance with some embodiments.

FIG. 4 illustrates a transmitter according to some embodiments of the inventions.

Fig. 5 illustrates an algorithm that may be performed in a transmitter such as that shown in fig. 4 in accordance with some embodiments of the present invention.

These figures are discussed in further detail below.

Detailed Description

In the following description, specific details of some embodiments of the invention are set forth. It will be apparent, however, to one skilled in the art, that some embodiments may be practiced without some or all of these specific details. The specific embodiments disclosed herein are intended to be illustrative rather than restrictive. Although not specifically described herein, those of ordinary skill in the art will recognize other elements that are within the scope and spirit of the present disclosure.

The description and drawings illustrate aspects and embodiments of the invention and should not be taken as limiting the invention as defined by the claims. Various changes may be made without departing from the spirit and scope of the description and claims. In some instances, well-known structures and techniques have not been shown or described in detail to avoid obscuring the invention.

Elements and their associated aspects, which have been described in detail with reference to the embodiments, may, where applicable, be included in other embodiments in which they are not specifically shown or described. For example, if an element is described in detail with reference to one embodiment and not described with reference to the second embodiment, it may still be claimed as being included in the second embodiment.

According to embodiments of the present invention, the transmitter may comprise a plurality of transmit coil configurations and it may be determined which configuration to use with respect to a particular receive coil of the wireless power receiver by monitoring a quality factor Q coupled between each of the transmit coil configurations and the receive coil. Due to the presence of the Rx device, which has been placed above the Tx base, the Q factor can be detected from the change in impedance facing the Tx coil. The change in the Q factor of each transmit coil as the receive coil is placed in close proximity to the transmit coil configuration determines which transmit coil configuration to use for transmission.

Fig. 1 illustrates a simplified wireless power system 100 according to some embodiments of the invention. The system 100 includes a wireless power transmitter 102 and a wireless power receiver 110. The wireless power transmitter 102 and the wireless power receiver 110 are housed in separate devices, such as: a fixed charging station and a mobile device, or two mobile devices. The wireless power transmitter 102 may be part of a stationary charging device, while the wireless power receiver 110 may be included in a wireless device.

As illustrated in fig. 1, the device may be arranged to comprise a transmitter or a receiver. The transmitting device 100 includes a wireless power transmitter 102 and a transmit coil 106. The receiver 110 includes a wireless power receiver 110 and a receive coil 108. However, depending on the context, in some embodiments it may be useful for a device to be able to both transmit and receive wireless power, and thus the device will include both the transmitter 102 and the receiver 110. In some embodiments, a device may include both a transmitter and a receiver, however in a given context, one device transmits power and the other device receives power.

As illustrated in fig. 1, a wireless power transmitter 102 is coupled to receive power from a power source 104. The wireless power transmitter 102 drives the transmit coil 106 to generate a time-varying electromagnetic field at a particular frequency, which is also the switching frequency of a driver coupled to the transmit coil 106. The receive coil 108 of the wireless power receiver 110 couples with the electromagnetic field generated by the transmit coil 106 of the wireless power transmitter 102 to receive the wireless power transmitted at the same particular frequency. As illustrated in fig. 1, the receive coil 108 is coupled to a wireless power receiver 110, the wireless power receiver 110 receiving power from the receive coil 108 and providing power to a load 112. The wireless power transmitter 102 may be configured to generate a time-varying electromagnetic field in the presence of a wireless power receiver 110, the wireless power receiver 110 configured to receive wireless power transmitted by the wireless power transmitter 102. The elements of the wireless power transmitter 102 and the wireless power receiver 110 may vary in size and shape to meet the power requirements and physical positioning of the wireless power system 100.

As discussed above, the wireless power receiver 110 recovers power from the time-varying electromagnetic field and generally provides a DC power input to the load 112 of the device that includes the wireless power receiver 110 and the receive coil 108. When a device is near the wireless power transmitter 102, power is transferred. In some cases, the load 112 may include a battery charger and the device includes a battery.

Some manufacturers are developing transmit coils that include multiple concentric coils to provide efficient wireless power transfer between the transmitter 102 and the receiver 110 depending on the size of the receive coil 108. As such, the transmit coil 106 includes multiple concentric coils that may be used to transmit power, according to some embodiments. Each of the concentric coils may be used with a receive coil 108 suitable for various devices. For example, the receive coil 108 in the wearable device has a much smaller diameter than the receive coil 108 for a telephone device or tablet device. Thus, because efficient wireless transmission occurs with a receive coil 108 having a larger diameter than the transmit coil 106, the transmit coil 106 may be configured to provide a coil that is suitable for the particular receive coil 108. For example, in one configuration, the transmit coil 106 may include a wearable coil as a center coil. The wearable center coil is surrounded by a phone charging coil suitable for use in a smart phone. The telephone coil may in turn be surrounded by a larger diameter tablet computer coil. In some embodiments, the coils are concentric within each other. In some embodiments, the coils may be combined such that the transmit coil diameter is larger for larger receiving devices having larger diameter receive coils 108. Each successively larger RX unit (watch, phone, tablet) will also include the metal inherent in the design. These metals will also be detectable by the Tx coil in the Q factor test. With the information from each coil, the size of the currently placed Rx can be determined with reasonable assurance.

Fig. 2A, 2B, and 2C illustrate such an arrangement according to some embodiments. As illustrated in fig. 2A, the transmit coil 106 includes a plurality of concentric coils: coil 202, coil 204, and coil 206. Coil 202 has the smallest diameter, coil 206 has the largest diameter, and coil 204 has an intermediate diameter between the diameter of coil 202 and the diameter of coil 206. Embodiments of the present invention may include any number of concentric coils greater than 2. Three coils are illustrated here for ease of illustration: coil 202, coil 204, and coil 206. For example, as discussed above, coil 202 may be a wearable transmit coil, coil 204 may be a telephone transmit coil, and 206 may be a tablet computer transmit coil. In some embodiments, coils 202, 204, and 206 may be completely separate coils. In some embodiments, coil 202, coil 204, and coil 206 may be coupled together for use.

Fig. 2A illustrates the operation of the transmit coil 106 in proximity to the receive coil 108, the receive coil 108 having a diameter greater than the diameter of the coil 202 but less than the diameters of the coil 204 and the coil 206. In this case, efficient power transmission occurs by powering coil 202 without powering coil 204 and coil 206. In this case, the receive coil 108 may represent a receive coil of a wearable device, and the coil 202 may be referred to as a wearable transmit coil.

Fig. 2B illustrates the operation of the transmit coil 106 in proximity to the receive coil 108, the receive coil 108 having a diameter greater than the diameter of the coil 204 but less than the diameter of the coil 206. In this case, efficient power transmission occurs by powering coil 204 without powering coil 206 or coil 202. In some embodiments, the coil 202 and the coil 204 may be coupled in series, and both the coil 202 and the coil 204 are powered to provide a magnetic flux through the receive coil 108. In this case, the receive coil 108 may represent a telephone receive coil of a mobile telephone, and the coil 204 may be referred to as a telephone transmit coil.

Fig. 2C illustrates the operation of the transmit coil 106 in proximity to the receive coil 108, the receive coil 108 having a diameter greater than the diameter of the coil 206. In this case, efficient power transmission occurs by powering coil 206 without powering coil 204 and coil 202. In some cases, the coil 202, the coil 204, and the coil 206 may be coupled in series, and the coil 202, the coil 204, and the coil 206 may be powered to provide a magnetic flux through the receive coil 108. In this case, the receive coil 108 may represent a tablet computer receive coil of a tablet computer, and the coil 206 may be referred to as a tablet computer transmit coil.

As the receive coil 108 is placed close to the transmit coil 106, a quality factor Q between each of the

coils

202, 204, and 206 may be determined. Thus, as discussed below, the variation in Q between coils may be used to determine which coil is configured for powering of the wireless power transfer as compared to Q measured in the absence of a foreign object.

Fig. 3A and 3B illustrate example coil configurations that may form the transmit coil 106. As illustrated in fig. 2A, 2B, and 2C, the coil 202, the coil 204, and the coil 206 are concentric coils. As shown in fig. 3A, each of coil 202, coil 204, and coil 206 is completely separate and separately powered. As shown in fig. 3B, coil 202, coil 204, and coil 206 may be coupled in series. Each of coil 202, coil 204, and coil 206 may be separately powered or powered in a series combination. However, depending on the context, in some embodiments, coil 202, coil 204, and coil 206 may also be powered simultaneously, such that coil 202 may be powered, coil 202 and coil 204 may be powered together, or coil 202, coil 204, and coil 206 may be powered together.

In current systems, the multi-coil design does not include overlapping coils, each of the coils is separate and not concentric, and the signal strength can be easily used to determine on which coil the Rx device is placed. With concentrically placed coils as illustrated in fig. 2A, 2B and 2C (each coil being inside or surrounding another coil), the signal strength cannot be reliably used to determine the coil that should be used to charge the receiving device. Furthermore, connecting (e.g., using in-band communication) and using an identification process or configuration process to decide what device was placed on the transmit coil 106, then if the wrong transmit coil was initially used, switching the coil to the correct coil or coil configuration again takes too long. Accordingly, embodiments of the present invention detect characteristics of the device including the receiver 110, and in particular characteristics of the receive coil 108, to determine which of a plurality of coil configurations in the transmit coil 106 is used for powering the wireless power transfer. This determination may be done before starting the PING procedure and connecting to the receiver 110.

Fig. 4 illustrates an example of the transmitter 102 coupled to the configuration of the transmit coil 106 shown in fig. 3A. As illustrated in fig. 4, the transmitter 102 includes: a controller 402, a driver 404, and a switching network 406. The controller 402 may be a microcontroller or other processor-based controller. For example, the controller 402 may include: a processor, volatile and non-volatile memory, and all supporting circuitry to receive data, execute instructions, and provide control signals. As illustrated in fig. 4, the controller 402 receives two signals AC1 and AC2 from the driver 404 and provides control signals (in this case VG1, VG2, VG3, and VG4) to the driver 404 and to the switching network 406. The controller 402 may further include analog-to-digital converters to receive the voltages AC1 and AC2 and digitize the voltages AC1 and AC 2.

The driver 404 receives control signals (VG 1, VG2, VG3, and VG4 in this example) and provides an AC voltage for driving the transmit coil 106. In the specific example illustrated in fig. 4, the driver 404 is a full bridge DC to AC inverter having: transistor 408 and transistor 412 coupled in series between the input voltage Vin and ground, and transistor 410 and transistor 414 coupled in series between the input voltage Vin and ground. The transistor 408, the transistor 412, the transistor 410, and the transistor 414 are driven by the gate voltage VG1, the gate voltage VG2, the gate voltage VG3, and the gate voltage VG4, respectively, to provide an AC voltage between the node AC1 and the node AC 2. Voltage AC1 and voltage AC2 are input to controller 402, and voltage AC1 and voltage AC2 are applied to switching network 406 to drive transmit coil 106. In some embodiments, the driver 404 may be a half-bridge inverter. For example, transistor 408 and transistor 412 are not present in the half-bridge configuration, and AC1 may be grounded. AC2 is then switched between Vin and ground in transistor 410 and transistor 414.

The switching network 406 receives control signals from the controller 402 as well as the voltage AC1 and the voltage AC 2. In accordance with the control signal, the switching network 406 couples one of the configurations of the coil 106 to receive the voltage AC1 and the voltage AC2, thereby driving the configuration. In some embodiments, the unused coil configuration may be disabled, e.g., grounded or left floating and not connected to the power drive signal, so as not to interfere with power transmission from the activated coil configuration.

As further illustrated in fig. 4, coil 202, coil 204, and coil 206 are coupled in series with capacitor 416, capacitor 418, and capacitor 420, respectively, such that each configuration forms a resonant tank. In some embodiments, capacitor 416, capacitor 418, and capacitor 420 are separate capacitors that are matched to coil 202, coil 204, and coil 206, respectively. In some embodiments, the configuration shares one or more capacitors controlled by the switching network 406 to form separate oscillating circuits.

The Q measurement may be performed by the controller 402 and is an indirect reflection of the size of an object placed over the transmit coil 106. For example, by monitoring the voltage between AC1 and AC2 and the current through each coil configuration in transmit coil 106, the Q factor may be determined. The Q-factor measurement may be used to determine the physical dimensions of the object. The Q factor reflected at the transmit LC tank circuit formed by each configuration of the coils in the transmit coil 106 may be determined by the newly placed Rx device receive coil 108. The Q-factor calibration is obtained without placing an object (including the receive coil 108) close to the transmit coil 106 and the results are saved to a non-volatile memory in the controller 402. Then, a Q-factor measurement may be performed and compared to stored Q-factor measurements in order to quickly determine the dimensions of the object to detect the appropriate coil to select for charging.

Fig. 5 illustrates an algorithm 500 for determining which coil configuration to use when the transmit coil 108 is placed in close proximity to the transmit coil 106. As illustrated in fig. 5, the algorithm 500 begins at a start 502, where the presence of a receive coil 108 in proximity to a transmit coil 106 is detected. In step 504, a Q factor configured for each coil of the transmit coils 106 is determined. For example, in transmit coil 106 illustrated in fig. 3A, the Q factor for each of coil 202, coil 204, and coil 206 in combination with a corresponding capacitor is determined in controller 402 by monitoring voltage AC1 and voltage AC2 and the current passing through each of coil 202, coil 204, and coil 206.

For convenience, in the presence of receive coil 108, the Q-factor of coil 202 may be denoted as QM1, the Q-factor of coil 204 may be denoted as QM2, and the Q-factor of coil 206 may be denoted as QM 3. The standard Q-factor is measured in the absence of foreign objects, which is stored in the non-volatile memory of the controller 402 during an initial qualification test (qualification) of the transmitter 102, and may be expressed as: QS1 for coil 202, QS2 for coil 204 and QS3 for coil 206.

In step 506, the determined Q factor is compared to a stored Q factor without foreign objects and to each measurement collected by the transmit coil when the transmitter measures Q with the RX unit placed to allow the transmitter to interpret the size of the receiver currently placed. Thus, a Q-factor difference for each coil configuration is determined. For coil 202, Ql — QS1-QM 1; Q2Q QS2-QM2 for coil 204; and Q3Q 3-QM3 for coil 206. Based on Q1, Q2, and Q3, the coil configuration (coil 204, coil 206, or coil 206) for power supply is determined.

Using the differences in these calculated qs (Q1, Q2, and Q3), it is determined which coil configuration of the transmit coil 106 should be used to transmit power to the receive coil 108. In step 508, if Q1 represents a high change, Q2 represents a low to medium change, and Q3 represents a low change, the algorithm 500 proceeds to step 510, where the coil 202 is powered. For example, if a watch is placed over the transmit coil 106, the center coil (watch coil) will have a high negative change in the coil, the middle coil (phone coil) may have a negative change in the Q-factor, and the outer coil (tablet coil) may have a low change in the Q-factor. In this scenario, the watch is identified by the process, and the watch coil is powered. If the conditions of Q1 being high, Q2 being medium or low, and Q3 being low are not met, the algorithm 500 proceeds to step 512.

In step 512, if Q1 represents a high change, Q2 represents a high change, and Q3 represents a medium or low change, the algorithm 500 proceeds to step 514, where the coil 204 is activated. In some cases, both coil 202 and coil 204 may be activated. In a specific example, the target (receive coil) 108 may be a telephone. In this case, the watch coil 202 detects a high Q factor change, the phone coil 204 indicates a high Q factor change, and the tablet computer coil 206 detects a medium to low Q factor change. In this case, the telephone coil 204 is used for wireless power transfer. If such a condition is not met, the algorithm 500 proceeds to step 516.

In step 516, if Q1 represents a high change, Q2 represents a high change, and Q3 represents a high change, the algorithm 500 proceeds to step 518, where the coil 206 is activated. In some embodiments, all of

coils

202, 204, and 206 may be activated. In a specific example, the target (receiving coil) 108 may be a tablet computer. In this case, as discussed above, the watch coil 202 exhibits high Q factor variation, the phone coil 204 exhibits high Q factor variation, and the tablet computer coil 206 exhibits high Q factor variation. In this case, the tablet computer is selected for transmission.

If the algorithm 500 reaches step 520, no condition applies. The algorithm 500 concludes that there are no receive coils 108 and the algorithm 500 exits. In the event that the Q-factor detection concludes that some type of receiver, but then the transmitter determines that the selection is erroneous, the transmitter may be configured to alter the transmitter's decision based on the wireless power characteristics obtained through communication with the currently placed receiver. For example, the transmitter may determine the original selection error based on an identification reported by the receiver, or based on the power requirement not being met. For example, if excess power is sent, the transmitter may switch to the next smaller available coil. If insufficient power is sent, the transmitter may select the next larger coil.

The above detailed description is provided to illustrate specific embodiments of the invention and is not intended to be limiting. Various variations and modifications are possible within the scope of the invention. The invention is set forth in the appended claims.

Claims

1. A wireless power transmitter, comprising:

a transmit coil comprising a plurality of concentric coils;

a switching circuit coupled to the plurality of concentric coils;

a driver coupled to provide a voltage to the switching circuit; and

a controller coupled to the switching circuit, the controller providing a control signal to the switching circuit such that the voltage is selected to be provided across one or more of the plurality of concentric coils depending on a Q factor measured in the presence of a receive coil.

2. The transmitter of claim 1, wherein each of the plurality of concentric coils is a separate coil.

3. The transmitter of claim 1, wherein the plurality of concentric coils are coupled in series.

4. The transmitter of claim 1, wherein the controller executes instructions to:

measuring a Q factor for each of the plurality of concentric coils to form a measured Q factor;

determining a difference between the measured Q-factor and a set of standard Q-factors, the set of standard Q-factors for each of the plurality of concentric coils; and

selecting which of the plurality of concentric coils to use based on the difference.

5. The transmitter of claim 4, wherein the plurality of concentric coils comprises: an inner coil, a middle coil and an outer coil.

6. The transmitter of claim 5, wherein the difference comprises: an inner coil difference, a middle coil difference, and an outer coil difference, and the controller determines which of the plurality of concentric coils to use by:

selecting the inner coil when the inner coil difference is high, the middle coil difference is low or medium, and the outer coil difference is low;

selecting the middle coil when the inner coil difference is high, the middle coil difference is high, and the outer coil difference is low or medium; and

selecting the outer coil when the inner coil difference is high, the middle coil difference is high, and the outer coil difference is high.

7. The transmitter of claim 5, wherein the difference comprises: an inner coil difference, a middle coil difference, and an outer coil difference, and the controller determines which of the plurality of concentric coils to use by:

selecting a series combination of the middle coil and the inner coil when the inner coil difference is high, the middle coil difference is high, and the outer coil difference is low or medium; and

selecting a series combination of the outer coil, the middle coil, and the inner coil when the inner coil difference is high, the middle coil difference is high, and the outer coil difference is high.

8. The transmitter of claim 5, wherein the inner coil has a diameter suitable for use with a wearable device, the middle coil has a diameter suitable for use with a telephone, and the outer coil has a diameter suitable for use with a tablet computer.

9. A method of operating a wireless power transmitter, comprising:

determining a measured Q factor for each of a plurality of configurations of concentric transmit coils;

determining a difference between each of the measured Q-factors and a standard Q-factor; and

selecting one of the plurality of configurations based on the difference.

10. The method of claim 9, wherein the plurality of configurations of concentric transmit coils comprises a plurality of independently driven concentric coils.

11. The method of claim 9, wherein the plurality of configurations of concentric transmit coils comprises a combination of one or more series couplings of a plurality of concentric coils.

12. The method of claim 9, wherein the plurality of configurations comprises: an inner coil, a middle coil and an outer coil.

13. The method of claim 12, wherein the difference comprises: an inner coil difference, a middle coil difference, and an outer coil difference, and wherein selecting one of the plurality of configurations comprises:

14. The method of claim 12, wherein the difference comprises: an inner coil difference, a middle coil difference, and an outer coil difference, and wherein selecting one of the plurality of configurations comprises:

15. The method of claim 12, wherein the inner coil has a diameter suitable for use with a wearable device, the middle coil has a diameter suitable for use with a phone, and the outer coil has a diameter suitable for use with a tablet computer.

16. The method of claim 9, further comprising:

determining whether the one of the plurality of configurations is unsuitable; and

selecting a different one of the plurality of configurations if the one of the plurality of configurations does not fit.

17. The method of claim 16, wherein determining comprises: receiving an actual identification that is inconsistent with the one of the plurality of configurations.

18. The method of claim 16, wherein the one of the plurality of configurations is determined to be unsuitable when a power requirement of a receiver cannot be met.

19. The method of claim 18, wherein the different configuration comprises a next size coil if the power requirement of the receiver cannot be met with the one of the plurality of configurations.